Identification of vibration sources in optical disk drives using transfer path analysis

In complicated structures it is difficult to determine causes of vibration because of non-linearity and variation of the system. Though Operating vibration signal has a strong similarity to dynamic characteristics of the structure in static state, it is too early to conclude that resonance of the structure brings out vibration of the structure without source identification. In vibration source identification it is important to decide not only the location and the number of sources but also rankings of sources. With this information one can know vibration generation mechanisms and devise counter plans. This research demonstrates the application for vibration source identification in optical disk drives. There are many vibration sources such as the external disturbance, the disk vibration, airflow, the motor vibration, and the chassis vibration in optical disk drives. These vibration sources are inputs of the system. And focus error signal is an output of the system. Therefore optical disk drive can be defined as a MISO system. In this research, the multiple coherence function between the output and all inputs is evaluated experimentally. The partial coherence functions are used to show which source is the major sources of focus error signal.